3 Easy Ways to Easily Remove Inaudible High Pitched Noise from Audio

I recently heard of someone with a very unique audio problem. An audio engineer had recorded some live music directly to his computer and used an old CRT monitor to monitor the recording. Everything came out fine, but when he played the recordings back for review, his children said that there was a high pitched whine in the song that he couldn’t hear. Now instead of having a perfectly crafted song ready for sale, the engineer had to figure out a way to get rid of noise that he couldn’t even hear.

The inability to hear high frequency noises is called presbycusis. It is occurs naturally in adult 30 years and older and it means that you can’t hear anything in the 14 to17 kilohertz range. This isn’t a problem for most people because dialog and common sound are far below this range. Children, however, can here these frequencies very clearly and can be harm by them if heard in excess or at loud volumes.

Fortunately, most audio programs have handy tools to help combat this called a spectral frequency view. This view gives you a visual representation of the sound you are editing so you can edit with your eyes and not your ears. This makes removing what you can’t hear a snap!

In your favorite audio editing program open up the file that has the noise you want removed, then switch to the spectral view. You have to consult the program’s help file to find out how to do this.

Above is a the linear spectral view in Adobe Audition. As you can see, there is a bright horizontal line at the top half of the left and right channel. That line represents the high pitched sound that young people can hear but adults can’t. To remove the sound, use the marquee tool (the square made form dashed lines on the main tool bar, or just press M ) Then select the horizontal line in the spectral view.

 

Once you have selected the high pitched noise, you can use floating amplitude dial above the selection to turn the volume down to 0db, or you could just press the delete key on your keyboard.

 

After Audition finishes saving the undo data and redrawing the spectral view, your file should have a blank horizontal line in the top half of each channel.

To prevent getting inaudible high pitched noise in your audio files you may want to do some of the following:

• Always use grounded equipment and outlets. This will prevent some noise from being recorded.
• Use power stripes that have RF filters. These will also prevent some noise from being recorded. The faint dark horizontal line in the above spectral pictures is from the noise that the power strips I use blocked. You can buy some nice but cheap Belkin surge protected and RF filtered power strips at Google’s Product Search.
• Use LCD monitors instead of CRT monitors. In my experience, LCD monitors don’t interfere with and type on computer based recording.
• Use cables that have ferrite beads (the round cylinders that most USB and laptop power cord have at the ends). If you don’t have cables wit ferrite beads built in, you can buy ones that clip on to cables from The Shack, or from many on-line retailers.